This invention relates to a method of forming condensed phosphates and amidophosphates in an aqueous solution. More specifically, this invention relates to a method of forming condensed phosphates, such as sodium trimetaphosphate, and amidophosphates in an aqueous solution or suspension using sulfamides and phosphate ions.
Condensed phosphates are characterized by the presence of at least one P--O--P linkage which is formed by the dehydration of orthophosphates or the dehydration of less highly condensed phosphates. Condensed phosphates are typically made in industry by heating orthophosphates to very high temperatures to drive off water of constitution. U.S. Pat. No. 3,367,737 discloses a method of manufacturing an alkali metal polyphosphate, such as sodium trimetaphosphate, by calcining an inorganic alkali metal phosphate, such as monosodium orthophosphate, at a temperature of from about 450.degree. to 620.degree. C. U.S. Pat. No. 3,382,037 discloses a method to produce sodium trimetaphosphate by continuously feeding an aqueous solution of sodium phosphate through a reaction zone while introducing combustion gases at a temperature of from about 800.degree. to 850.degree. C.
The condensation of phosphates is also chemically effected. V. M. Clark, et. al., J. Chem. Soc. (C), 1969, 233, disclose a method of chemically dehydrating phosphates with reagents such as chloroquinones to form condensed phosphates. Chemical dehydrations of this type are extremely sensitive to traces of moisture and sufficient water completely inhibits the reaction E. J. Griffith, et. al., J. Amer. Chem. Soc., 89, 2884 (1967), disclose rearrangements of condensed phosphates in aqueous solution, such as the formation of cyclic trimetaphosphate from hexaphosphate. Although one new P--O--P linkage is formed, it is at the expense of another with no net change in the degree of condensation.
Typically, the formation of amidophosphates requires anhydrous conditions. G. M. Kosolapoff, Organophosphorus Compounds, John Wiley and Sons, 1950. 293, discloses the reaction of triethyl phosphate and ammonia in ether or alcohol to form diethylamidophosphate. Also the reactions of secondary phosphites with primary or secondary amines in the presence of aliphatic polyhalide to from amidophosphates are disclosed. D. E. C. Corbridge, Phosphorous, An Outline of its Chemistry, Biochemistry and Technology, Third Edition, Elsevier, 1985, 291, discloses the reaction of ammonia with phenyl phosphodichlorides to form amidophosphates. O. T. Quimby, et.al., Z. Anorg. Allg. Chem., 296, 224(1958), disclose that small cyclic phosphates, such as trimetaphosphate, are an exception to the requisite anhydrous conditions, and react with aqueous ammonia to form monoamidotriphosphate.
Deriviatized phosphates are known to form condensed phosphates under controlled hydrolytic conditions. O. T. Quimby, et. al., J. Amer. Chem. Soc., 82, 1099 (1960), disclose the condensation of amidophosphates in aqueous media to form condensed phosphates. G. M. Kosolaphoff, Organophosphorus Compounds, John Wiley and Sons, Inc., New York, 1950, Chap. 12, discloses condensation reactions using halophosphates and/or phosphate esters.
None of the above references disclose a method preparing condensed phosphates and amidophoshates in an aqueous solution from sulfamides and phosphate ions.